A note about alternative engine choices: Although there may be other viable engine choices for Sonex Aircraft, LLC airframes, only approved engine installations have been engineered and tested by Sonex Aircraft, LLC, and have proven to offer outstanding, reliable performance without compromising the flight characteristics or useful load of the airframes. When installed according to Sonex-provided documentation, the user of an approved engine can anticipate a trouble-free installation proven by thousands of flight hours, as well as full customer support and on-going serviceabilty.
Customers should not underestimate the vast amounts of time, money, and effort that go into alternative engine development and installation. Any customer choosing to use an unsupported engine installations are true "experimenters". Sonex Aircraft, LLC will not offer firewall-forward technical support for unapproved engine installations. Your choice of an alternative engine may also result in insurability problems. As a potential builder, you must educate yourself on the true impact of your engine choice before embarking on an alternative engine installation. The list of issues that should be considered include but are not limited to: Installation support (cowl, engine mount, cooling), installed weight, reliability, serviceability, impact on flight qualities and useful load of airframe, and availability/cost of insurance. Sonex Aircraft engine installations must not exceed 200 lbs total weight forward of the firewall. Any builder considering use of a heavier installation should take notice of the important information contained in our Gross Weight Advisory (LSA Compliance and Safety) Letter.
Sonex staff have been involved in the aircraft and engine business for over 40 years and we are constantly watching the engine market for emerging products. If a new, viable powerplant emerges which fits our needs and philosophy it will be offered only after it has been thoroughly tested on factory aircraft. If you have any questions about your engine choice, please feel free to contact us.